Hydrogen is an important feedstock for the manufacture of chemicals and as a clean fuel in combustion engines. It finds uses in activities such as the manufacture of fertilizers, petroleum processing, methanol synthesis, production of chemicals and fuels, annealing of metals and producing electronic materials. In the foreseeable future, emergence of technology will extend the use of hydrogen to domestic and vehicle applications.
Typically, the primary synthetic routes for the production of hydrogen have consisted of catalytic steam reforming of methane, C2-C4, natural gas, LPG (liquefied petroleum gas), naphtha or other light hydrocarbons. In one method used by the art to produce hydrogen by steam reforming, a methane and steam feed stream is passed through catalyst filled tubes disposed within a reactor or reformer. Fuel and air are combusted outside of the tubes in the reformer to provide heat for the endothermic catalytic reaction taking place within the tubes at about 800° C. In this process, the mixture of methane and steam is converted to a gaseous stream consisting primarily of hydrogen (about 68%) and CO2 (about 21.7%), CO (about 1.5%) and H2O (about 8.8%).
Other routes have reportedly used the partial oxidation of heavy oil residues and coal gasification from these starting materials. Increased interest in fuel hydrogen production requires the development of economically and environmentally sustainable processes that compete with processes involving derivation of hydrogen gas from hydrocarbons obtained from petrochemical and natural gas sources. The world's supply of petroleum is being depleted at an increasing rate. Eventually, demand for petrochemical derived products will outstrip the supply of available petroleum. When this occurs, the market price of petroleum and, consequently, petroleum derived products will likely increase, making products derived from petroleum more expensive and less desirable. As the available supply of petroleum decreases, alternative sources and, in particular, renewable sources of comparable products will necessarily have to be developed. One potential renewable source of petroleum derived products is products derived from bio-based matter, such as agricultural and forestry products. Use of bio-based products may potentially counteract, at least in part, the problems associated with depletion of the petroleum supply.
The replacement of petrochemicals and petroleum derived products with products and/or feed stocks derived from biological sources (i.e., bio-based products) offers many advantages. For example, products and feed stocks from biological sources are typically a renewable resource. As the supply of easily extracted petrochemicals continues to be depleted, the economics of petrochemical production will likely force the cost of the petrochemicals and petroleum derived products to higher prices compared to bio-based products. In addition, companies may benefit from the marketing advantages associated with bio-derived products from renewable resources in the view of a public becoming more concerned with the supply of petrochemicals.
Renewable lignocellulosic biomass feedstocks represent alternative feedstocks for the production of hydrogen. Recent developments in this area have reported the use of renewable carbohydrate feedstocks that are derived from dilute sugar streams and lignocellulosics (i.e. soft and hardwoods, crop residues such as straws, hulls, and/or fibers) to produce hydrogen using thermochemical processes such as pyrolysis and/or gasification.
One problem of using biomass feedstocks with a steam reformer is the increased coking activity on the steam reformer catalyst due to the feedstock. This coking activity causes premature degradation of the steam reformer catalyst. There exists a need for a process to reducing the coking activity inside a steam reformer catalyst.